Geological History of Crater Lake
The best views of the rim are obtained from a boat on the lake, which affords an opportunity to examine in detail the position and structure of the cliffs.
They are composed wholly of volcanic conglomerate and streams of lava arranged in layers, as shown in figure 12, that dip into the rim and away from the lake on all sides. Both forms of volcanic material are well exposed on the trail descending the inner slope, and, although most of the cliffs are of lava, many are of conglomerate.
On arriving at the water’s edge the observer is struck with the fact that there is no beach. (See fig. 14.) The steep slopes above the surface of the lake continue beneath its waters to great depths. Here and there upon the shore, where a rill descends from a melting snow bank near the crest, a small delta deposit makes a little shallow, turning the deep-blue water to pale green.
